ab8500_fg: Fix error return code

Initialize return variable before exiting on an error path.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}

// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>

drivers/power/ab8500_fg.c

@@ -2506,6 +2506,7 @@ static int __devinit ab8500_fg_probe(struct platform_device *pdev)
 	di->fg_wq = create_singlethread_workqueue("ab8500_fg_wq");
 	if (di->fg_wq == NULL) {
 		dev_err(di->dev, "failed to create work queue\n");
+		ret = -ENOMEM;
 		goto free_device_info;
 	}